What does it mean when the heater is turned on with A/C?

[StephanieRose]

Turning on the heater with A/C means the car's compressor is running, which will additionally increase the vehicle's fuel consumption. Reasons why turning on the heater with A/C increases fuel consumption: In A/C mode, since the car's air conditioning compressor is always in operation, it will inevitably lead to increased fuel consumption and additional engine load. When using the heater, the A/C switch should be turned off to prevent the compressor from running and causing extra fuel consumption during heating. Function of A/C: A/C is the abbreviation for air conditioning, with its full name being air condition, which can be understood as air control or air adjustment. It achieves the purpose of cooling or heating through different operation modes of the air conditioning compressor, hence it has dual meanings of cooling and heating. However, in cars, since the heating function of the vehicle's air conditioning is accomplished through the heat from the engine's cooling water and the heating wires on the glass, A/C only has the single meaning of cooling in this context.